refactor: switch Unix sockets from STREAM to DGRAM mode

- Change net.Listen("unix") to net.ListenUnixgram("unixgram")
- Replace connection-based Accept() with ReadFromUnix() datagram reading
- Remove connection limiting semaphore (not needed for DGRAM)
- Update tests with datagram-specific tests
- Socket permissions default to 0666 (world read/write)

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

internal/adapters/inbound/unixsocket/source.go

@@ -1,7 +1,6 @@
 package unixsocket
 
 import (
-	"bufio"
 	"context"
 	"encoding/json"
 	"fmt"
@@ -18,10 +17,8 @@ import (
 )
 
 const (
-	// Maximum line size for JSON logs (1MB)
+	// Maximum datagram size for JSON logs (64KB - Unix datagram limit)
-	MaxLineSize = 1024 * 1024
+	MaxDatagramSize = 65535
-	// Maximum concurrent connections per socket
-	MaxConcurrentConnections = 100
 	// Rate limit: max events per second
 	MaxEventsPerSecond = 10000
 )
@@ -34,14 +31,13 @@ type Config struct {
 	SocketPermissions os.FileMode
 }
 
-// UnixSocketSource reads JSON events from a Unix socket.
+// UnixSocketSource reads JSON events from a Unix datagram socket.
 type UnixSocketSource struct {
 	config   Config
 	mu       sync.Mutex
-	listener  net.Listener
+	conn     *net.UnixConn
 	done     chan struct{}
 	wg       sync.WaitGroup
-	semaphore chan struct{} // Limit concurrent connections
 	stopOnce sync.Once
 	logger   *observability.Logger
 }
@@ -51,7 +47,6 @@ func NewUnixSocketSource(config Config) *UnixSocketSource {
 	return &UnixSocketSource{
 		config: config,
 		done:   make(chan struct{}),
-		semaphore: make(chan struct{}, MaxConcurrentConnections),
 		logger: observability.NewLogger("unixsocket:" + config.Name),
 	}
 }
@@ -66,7 +61,7 @@ func (s *UnixSocketSource) Name() string {
 	return s.config.Name
 }
 
-// Start begins listening on the Unix socket.
+// Start begins listening on the Unix datagram socket.
 func (s *UnixSocketSource) Start(ctx context.Context, eventChan chan<- *domain.NormalizedEvent) error {
 	if strings.TrimSpace(s.config.Path) == "" {
 		return fmt.Errorf("socket path cannot be empty")
@@ -83,12 +78,17 @@ func (s *UnixSocketSource) Start(ctx context.Context, eventChan chan<- *domain.N
 		}
 	}
 
-	// Create listener
+	// Create Unix datagram socket
-	listener, err := net.Listen("unix", s.config.Path)
+	addr, err := net.ResolveUnixAddr("unixgram", s.config.Path)
 	if err != nil {
-		return fmt.Errorf("failed to create unix socket listener: %w", err)
+		return fmt.Errorf("failed to resolve unix socket address: %w", err)
 	}
-	s.listener = listener
+
+	conn, err := net.ListenUnixgram("unixgram", addr)
+	if err != nil {
+		return fmt.Errorf("failed to create unix datagram socket: %w", err)
+	}
+	s.conn = conn
 
 	// Set permissions - fail if we can't
 	permissions := s.config.SocketPermissions
@@ -96,7 +96,7 @@ func (s *UnixSocketSource) Start(ctx context.Context, eventChan chan<- *domain.N
 		permissions = 0666 // default
 	}
 	if err := os.Chmod(s.config.Path, permissions); err != nil {
-		_ = listener.Close()
+		_ = conn.Close()
 		_ = os.Remove(s.config.Path)
 		return fmt.Errorf("failed to set socket permissions: %w", err)
 	}
@@ -104,13 +104,15 @@ func (s *UnixSocketSource) Start(ctx context.Context, eventChan chan<- *domain.N
 	s.wg.Add(1)
 	go func() {
 		defer s.wg.Done()
-		s.acceptConnections(ctx, eventChan)
+		s.readDatagrams(ctx, eventChan)
 	}()
 
 	return nil
 }
 
-func (s *UnixSocketSource) acceptConnections(ctx context.Context, eventChan chan<- *domain.NormalizedEvent) {
+func (s *UnixSocketSource) readDatagrams(ctx context.Context, eventChan chan<- *domain.NormalizedEvent) {
+	buf := make([]byte, MaxDatagramSize)
+
 	for {
 		select {
 		case <-s.done:
@@ -120,60 +122,35 @@ func (s *UnixSocketSource) acceptConnections(ctx context.Context, eventChan chan
 		default:
 		}
 
-		conn, err := s.listener.Accept()
+		// Set read deadline to allow periodic context checks
+		_ = s.conn.SetReadDeadline(time.Now().Add(100 * time.Millisecond))
+
+		n, _, err := s.conn.ReadFromUnix(buf)
 		if err != nil {
+			if netErr, ok := err.(net.Error); ok && netErr.Timeout() {
+				// Read timeout, continue to check context
+				continue
+			}
+			// Other errors (e.g., closed socket)
 			select {
 			case <-s.done:
 				return
 			case <-ctx.Done():
 				return
 			default:
+				s.logger.Warnf("read error: %v", err)
 				continue
 			}
 		}
 
-		// Check semaphore for connection limiting
+		if n == 0 {
-		select {
-		case s.semaphore <- struct{}{}:
-			// Connection accepted
-		default:
-			// Too many connections, reject
-			_ = conn.Close()
 			continue
 		}
 
-		s.wg.Add(1)
+		data := make([]byte, n)
-		go func(c net.Conn) {
+		copy(data, buf[:n])
-			defer s.wg.Done()
-			defer func() { <-s.semaphore }()
-			defer c.Close()
-			s.readEvents(ctx, c, eventChan)
-		}(conn)
-	}
-}
 
-func (s *UnixSocketSource) readEvents(ctx context.Context, conn net.Conn, eventChan chan<- *domain.NormalizedEvent) {
+		event, err := parseJSONEvent(data, s.config.SourceType)
-	// Set read deadline to prevent hanging
-	_ = conn.SetReadDeadline(time.Now().Add(5 * time.Minute))
-
-	scanner := bufio.NewScanner(conn)
-	// Increase buffer size limit to 1MB
-	buf := make([]byte, 0, 4096)
-	scanner.Buffer(buf, MaxLineSize)
-
-	for scanner.Scan() {
-		select {
-		case <-ctx.Done():
-			return
-		default:
-		}
-
-		line := scanner.Bytes()
-		if len(line) == 0 {
-			continue
-		}
-
-		event, err := parseJSONEvent(line, s.config.SourceType)
 		if err != nil {
 			// Log parse errors as warnings
 			s.logger.Warnf("parse error: %v", err)
@@ -360,8 +337,8 @@ func (s *UnixSocketSource) Stop() error {
 
 		close(s.done)
 
-		if s.listener != nil {
+		if s.conn != nil {
-			_ = s.listener.Close()
+			_ = s.conn.Close()
 		}
 
 		s.wg.Wait()

internal/adapters/inbound/unixsocket/source_test.go

@@ -2,6 +2,9 @@ package unixsocket
 
 import (
 	"context"
+	"fmt"
+	"net"
+	"os"
 	"testing"
 	"time"
 
@@ -391,3 +394,167 @@ func TestParseJSONEvent_TimestampFallback(t *testing.T) {
 		t.Error("expected non-zero timestamp")
 	}
 }
+
+func TestUnixSocketSource_StartStopDatagram(t *testing.T) {
+	tmpPath := "/tmp/test_logcorrelator_datagram.sock"
+	// Clean up any existing socket
+	os.Remove(tmpPath)
+
+	source := NewUnixSocketSource(Config{
+		Name:              "test_datagram",
+		Path:              tmpPath,
+		SourceType:        "B",
+		SocketPermissions: 0666,
+	})
+
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
+	defer cancel()
+
+	eventChan := make(chan *domain.NormalizedEvent, 10)
+
+	err := source.Start(ctx, eventChan)
+	if err != nil {
+		t.Fatalf("failed to start source: %v", err)
+	}
+
+	// Give socket time to start
+	time.Sleep(100 * time.Millisecond)
+
+	// Verify socket file exists
+	if _, err := os.Stat(tmpPath); os.IsNotExist(err) {
+		t.Error("socket file should exist")
+	}
+
+	// Stop the source
+	err = source.Stop()
+	if err != nil {
+		t.Errorf("failed to stop source: %v", err)
+	}
+
+	// Socket file should be cleaned up
+	time.Sleep(100 * time.Millisecond)
+	if _, err := os.Stat(tmpPath); !os.IsNotExist(err) {
+		t.Error("socket file should be removed after stop")
+	}
+}
+
+func TestUnixSocketSource_SendDatagram(t *testing.T) {
+	tmpPath := "/tmp/test_logcorrelator_send.sock"
+	os.Remove(tmpPath)
+
+	source := NewUnixSocketSource(Config{
+		Name:              "test_send",
+		Path:              tmpPath,
+		SourceType:        "B",
+		SocketPermissions: 0666,
+	})
+
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	eventChan := make(chan *domain.NormalizedEvent, 10)
+
+	err := source.Start(ctx, eventChan)
+	if err != nil {
+		t.Fatalf("failed to start source: %v", err)
+	}
+
+	// Give socket time to start
+	time.Sleep(100 * time.Millisecond)
+
+	// Connect and send a datagram
+	conn, err := net.Dial("unixgram", tmpPath)
+	if err != nil {
+		t.Fatalf("failed to dial socket: %v", err)
+	}
+	defer conn.Close()
+
+	data := []byte(`{"src_ip": "192.168.1.1", "src_port": 8080, "ja3": "test"}`)
+	_, err = conn.Write(data)
+	if err != nil {
+		t.Fatalf("failed to write: %v", err)
+	}
+
+	// Wait for event
+	select {
+	case event := <-eventChan:
+		if event.SrcIP != "192.168.1.1" {
+			t.Errorf("expected src_ip 192.168.1.1, got %s", event.SrcIP)
+		}
+		if event.SrcPort != 8080 {
+			t.Errorf("expected src_port 8080, got %d", event.SrcPort)
+		}
+	case <-time.After(2 * time.Second):
+		t.Error("timeout waiting for event")
+	case <-ctx.Done():
+		t.Error("context cancelled")
+	}
+
+	err = source.Stop()
+	if err != nil {
+		t.Errorf("failed to stop source: %v", err)
+	}
+}
+
+func TestUnixSocketSource_MultipleDatagrams(t *testing.T) {
+	tmpPath := "/tmp/test_logcorrelator_multi.sock"
+	os.Remove(tmpPath)
+
+	source := NewUnixSocketSource(Config{
+		Name:              "test_multi",
+		Path:              tmpPath,
+		SourceType:        "B",
+		SocketPermissions: 0666,
+	})
+
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	eventChan := make(chan *domain.NormalizedEvent, 100)
+
+	err := source.Start(ctx, eventChan)
+	if err != nil {
+		t.Fatalf("failed to start source: %v", err)
+	}
+
+	// Give socket time to start
+	time.Sleep(100 * time.Millisecond)
+
+	// Connect and send multiple datagrams
+	conn, err := net.Dial("unixgram", tmpPath)
+	if err != nil {
+		t.Fatalf("failed to dial socket: %v", err)
+	}
+	defer conn.Close()
+
+	for i := 0; i < 5; i++ {
+		data := []byte(fmt.Sprintf(`{"src_ip": "192.168.1.%d", "src_port": %d, "ja3": "test%d"}`, i+1, 8080+i, i))
+		_, err = conn.Write(data)
+		if err != nil {
+			t.Fatalf("failed to write datagram %d: %v", i, err)
+		}
+	}
+
+	// Wait for all events
+	received := 0
+	timeout := time.After(3 * time.Second)
+	for received < 5 {
+		select {
+		case event := <-eventChan:
+			received++
+			t.Logf("received event %d: src_ip=%s", received, event.SrcIP)
+		case <-timeout:
+			t.Errorf("timeout waiting for events, received %d/5", received)
+			goto done
+		case <-ctx.Done():
+			t.Error("context cancelled")
+			goto done
+		}
+	}
+
+done:
+	err = source.Stop()
+	if err != nil {
+		t.Errorf("failed to stop source: %v", err)
+	}
+}